[dm-devel] linux-next dm-thinp regression due to "bio: skip atomic inc/dec of ->bi_remaining for non-chains"
Mike Snitzer
snitzer at redhat.com
Wed May 13 19:28:27 UTC 2015
The device-mapper-test-suite (dmts) thinp tests no longer run due to
linux-block.git commit c4cf5261 ("bio: skip atomic inc/dec of
->bi_remaining for non-chains")
That commit has been the focus of some other work I have pending because
I was forced to adapt it due to bi_remaining no longer being accessible
directly. So it was surprising/interesting for this commit to take
center stage in the context of dm-thinp regression.
bios don't get submitted (simplest reproducer is the 'dd_benchmark' test
in the dmts thin-provisioning suite which just uses dd with oflag=direct
immediately after the DM thin device is created). The top-level DM
device stays at 100% utilization but no progress is made. Reverting
the commit in question resolves the problem.
But I'm able to use lvm2 to create thin devices that allow IO to
complete; so I haven't figured out what is so special about dmts (which
uses dmsetup directly instead of lvm2).
I'll see if I can figure out what might be happening... but would
welcome more eyes on this to see if anything stands out relative to the
dm-thin.c changes.
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